1. Field of the Invention
The invention relates to threaded tubular joints usable in oil and gas well drilling and production, such as tubing, casing, line pipe, and drill pipe, commonly known collectively as oilfield tubular goods. More particularly, the invention relates to a wear indicator for a tubular joint for connecting male (pin) and female (box) members.
2. Background Art
The use of threaded tubular connections for joining flow conduits in an end-to-end relationship to form a continuous flow path for transporting fluid under pressure is well known. Oilfield tubular goods all use threaded connections for connecting adjacent sections of conduit or pipe. Examples of such threaded end connections designed for use on oilfield tubular goods are disclosed in U.S. Pat. Nos. 2,239,942; 2,992,019; 3,359,013; RE 30,647; and RE 34,467, all of which are assigned to the assignee of the present invention.
FIGS. 1–2 illustrate a cross section of a wedge thread connection upon make-up of the pin member and the box member. As shown in FIG. 1, when pin member 10 engages box member 12 for the first time there exists no contact between external shoulder 14 of pin member 10 and external shoulder 16 of box member 12. In contrast, as shown in FIG. 2, when the connection is fully worn out, contact between external shoulder 14 of pin member 10 and external shoulder 16 of box member 12 exists upon make-up.
All existing connections used for the drilling of oil or gas wells are subject to torque shoulder wear from usage. In connections where the torque shoulder is a wedge thread form, such as the Hydril Tool Joint connection which is uniquely designed to absorb high torque while also forming a pressure seal, the connection is fully functional up to the point that the external shoulder of the pin member contacts the external shoulder of the box member. When this contact occurs the connection is worn out and needs to be re-cut. There is a need to be able to determine where any given pin or box connection is within its wear cycle prior to the connection being assembled in the field.
One method to determine the wear of the connection is using a function gage that is applied to the pin or box connection hand tight and recording standoff as an indicator or wear. This technique provides limited information in that the amount of damage and/or distortion to the wedge thread form on a used connection could cause the gage to stand off inconsistently when applied hand tight as compared to a power tight make-up position of the worn connection.